Electrical resistor



Feb. 21, 1961 o. F. BoYKlN ELECTRICAL RESISTOR 3 Sheets-Sheet 1 Filed Feb. 27, 1956 Hill 4/ u, W m #n M 9 wn. )2 7 a Wn \\2 0 7 n uw u, H X d w u M M /l r n u u im 6 M @f l 1 L ,v i wlillllleuud 4 Y f o l I /f/Mr mur? o L m f @u u /rl ffm H ,4 FMHNNHIIHHUL SM M e l m HUH o Y J 7- I lwllrallsmlHHnU q o 7- H E M//L w F 7 f w E W H y# )a /W/ 3 7 l s 5a l e u. 4 WLM HM /M l K fw Feb. 21, 1961 o. F. BOYKIN 2,972,726

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ELECTRICAL RESISTOR Filed Feb. 27, 1956 5 Sheets-Sheet 3 United States Patent O ELECTRICAL RESISTOR Otis F. Boykin, Chicago, Ill., assignor, by mesne assignments, to CTS Corporation, Elkhart, Ind., a corporation of Indiana Filed Feb. 27, 1956, Ser. No. 567,765

21 Claims. (Cl. 338-297) -This invention relates to an electrical resistor, and particularly to a high precision wire-type resistor.

Precision resistors as heretofore constructed have been diicult to manufacture and hence have been quite expensive. Commonly, precision resistors have been wound on bobbins or spools in spaced reversely wound sections. The bobbins have cores of relatively small diameter and are rotated at high speed to wind the wire thereon so that the wire is subjected to relatively great tension. It has been found that the strains resulting from the Winding operation cannot be economically fully relieved by heat treatment. Further the stretching of the wire during winding prevents accurate measurement of the wire as it is app-lied to the bobbin. The prior art spool or bobbin type resistors have also presented difiiculties due to the differential expansion and contraction of the wire relative to the bobbin in operation, and additionally the bobbin type resistor has very definite space requirements which make it unsuitable or disadvantageous in many applications.

Thepresent invention provides a precision type wire wound electrical resistor which can be readily adapted to different space requirements and configurations. The resistor will meet relatively stringent inductance requirements without the necessity for reverse winding as in the bobbin resistor, and may be made very cheaply and quickly without Wire strain. In bobbin type wire wound resistors, design changes to minimize the inductive effect usually bring about an increase in capacitance. However, with the present invention, the resisto-r can be designed to combine minimum inductive with minimum capacitive effects.

Resistors according to the present invention can be designed to provide tolerances as low as required, for example .02%, and can be designed to withstand relatively great accelerations and shocks and great temperature changes such as encountered in rocket ilight and the like. The resistors may be made in flat form for maximum heat transfer to flat mounting surfaces, or may be adapted to a wide variety of other mounting procedures. It is therefore an important object of the present invention to provide a precision wire wound resistor eliminating the conventional bobbin. It is a further object of the present invention to provide a novel resistance element in which the inductive effects associated with the element may be greatly reduced without the need for reverse winding of the wire.

A further object of this invention is to provide a novel electrical resistor which is simple and inexpensive to manufacture.

It is yet another object of the present invention to provide a resistance element whichis readily adaptable to different space and mounting requirements.

A still further object of the present invention is to provide a resistor which can withstand extreme accelerations and shocks and great temperature changes without 2 the danger of breakage of the fine resistance wire or other detrimental effects.

It is a more specific object of the present invention to provide a novel and improved terminal connection for a resistance wire.

Other and further objects, features and advantages of this invention will become apparent from the following detailed description taken in connection with the accompanying drawings showing certain preferred embodiments, in which:

Figure 1 is a more or less diagrammatic elevational view of a resistance element comprising an embodiment of the present invention;

Figure 2 is a greatly enlarged longitudinal sectional view of a portion of the resistance element of Figure 1, and illustrating somewhat diagrammatically the manner in which the wire may be wound in multiple layers on its support;

Figure 3 is a cross sectional view through the element shown in Figure 1;

Figure 4 is a plan view of a resistance element of the type shown in Figure 1 embedded in an insulated casing with the successive sections of the resistance element of Figure 1 connected to individual terminals;

Figure 5 is an elevational view of the structure of Figure 4 and illustrating the resistor secured to a flat heat conductive mounting surface;

Figure 6 illustrates the resistance element of Figure 1 with the supporting tape thereof folded to dispose the sections of the elements in such a way that the magnetic fields of adjacent sections 'opposed one another;

Figure 7 is an elevational view illustrating the resistance element of Figure 6 secured within an insulating casing and mounted against a suitable heat conductive surface;

Figure 8 illustrates a resistance element of the type shown in Figure 1 folded about a longitudinal axis and then wound arcuately on a spool, the resistance element having a length such that the opposite ends thereof will be in spaced relation after the element is wound on the spool; l

Figure 8a is a diagrammatic view of a single turn of resistance Wire in the resistor configuration of Figure 8;

Figure 9 is a cross sectional view taken generally along the line IX-IX of Figure 8;

Figure 10 is an elevational view of the structure of Figure 8 embedded within an insulating housing;

Figure 11 represents a resistance element such as shown in Figure l folded on a longitudinal axis and wrapped helically on an insulating tube;

Figure l2 illustrates a modification of the resistance element shown in Figure l, characterized by the fact that the tape or support upon which the winding sections are wound is severed between the sections and the sections are turned to dispose their magnetic axes in parallelism but with the magnetic elds of adjacent sections opposing one another;

Figure 13 is a perspective view of another form of resistor made in accordance with this invention;

Figure 14 is an enlarged longitudinal sectional View through the resistor of Figure 13;

Figure l5 is a fragmentary elevational view upon a larger scale of the resistanceelement shown in Figure 13;

Figure 16 is a perspective view of a resistance element, similar to that shown in Figure 15, wound into a spiral;

FigureI 17 is a cross sectional view taken on the line XVII-XVII of Figure 14;

Figure 18 is a greatly enlarged top plan view of the resistance element shown in Figure l5;

Figure 19 is a view similar to Figure 17 showing a aeraree resistor constructed with a resistance element that is folded into pleats in accordion fashion; and

Figure 20 is a perspective view of a pleated resistance element of the type used in the resistor shown 1n Figure 19.

As shown on the drawings:

The present invention concerns high precision electrical resistors which are formed by lengths of resistance wire preferably of the Order of .0006 inch to .010 inch in diameter. Wires of these sizes are commonly used for resistors of relatively small current ratings having resistance values from about .05 ohm to several megohms.

To form the resistance unit illustrated in Figures 1 to 3, a length of insulating material preferably in the form of a tube is placed on a mandrel in such a manner that a resistance wire 11 may be helically wound onto the tube as by rotation of the mandrel, preferably without the wire coming into contact with the surface of the mandrel itself. As the wire is wound onto the tube 10 the wire may be waxed or otherwise suitably cemented to the tube, and when the winding operation is complete the unit is removed from the mandrel. The tube 10 with the wire thereon is then flattened so that the tubev becomes a flat multi-ply tape and the convolutions of the winding are disposed in closely adjacent straight stretches. This iiattened multi-ply tape provides a very satisfactory and convenient support for the wire.

By way of specific example, the tube 1t) may be of polyethylene with the wall thickness for example of .002 inch. When the tube of polyethylene is flattened as indicated in Figure 3, it may form a tape having a width of 11A inches and a total thickness of .004 inch. Such a tape will be universally flexible and may be bent on any axis, and thus will accommodate a multiplicity of configurations as space or mounting requirements, inductive or capacitive limitations and the like may indicate.

Figure 2 illustrates, by way of example, the preferred manner in which the resistance wire 11 may be wound on the tube 10. In winding the resistance element illus- 'trated in Figure 2, the wire may be wound in contiguous helical turns in a iirst layer 13 along the tube 10 from left to right with the last turn in this first layer designated by the reference numeral 15. The next turn 16 of the wire is wound generally in a second layer 17 on top of or outwardly of the rst layer 13, but with the second layer 17 being laid down helically in the opposite direction from the first layer 13. The third layer indicated by the reference numeral 19 is wound from left to right as viewed in Figure 2 on top of the second layer 17 and has an end turn 20 which may be considered generally superposed on the end turns and 16 of the preceding layers. The fourth layer indicated generally by the reference numeral 23 proceeds from right to left and the outer laver indicated by the reference numeral 25 proceeds from left to right and terminates in an end turn Z6, for example.

The length of wire indicated at 27 in Figure 1 connects the turn 26 to a turn 29 in Figure 2 which is in a first layer 311. The layer 30 is wound helically in the direction from left to right iust as layer 13. Successive layers are indicated at 32, 34, 36 and 38 and are wound in the same manner as layers 17. 19, 23 and 25, respectivelv. 1t will be noted that the first turn in layer 13 and the first turn 40 of the outer or fifth laver 38 will have a maximum difference in potential. However, the capacitive effect associated with these turns 1S and 40 is minimized by the proper selection of the spacing indicated generally at x in Figure 1 between these turns.

It will be appreciated that the advantage of wind-ing the wire in multiple layers resides in thc reiative cornl pactness of the resultant resistor element, particularly as reflected in the length of the tube or tape 10 required for a given resistance value. The desired capacitive limitation may be achieved by properly spacing the multilayerV sections 43, 44, 45 and 46 shown in Figure 1, and

left hand side represented by the multiple layers 30, 32,

34, 36 and 38 in Figure 2. The conductive portion 48 of wire 11 has an insulating coating or covering thereon as indicated at 49 in Figure 2. The wire may be wound closely on the tube or tape 10 so that succeeding turns have their insulating coatings 49 in contact. The coatings will have the required thickness to properly insulate the turns of the wire taking into account the fact that the turns such as 16 and 20 will have a potential difference many times greater than the potential difference between successive turns such as 1S and 16, the difference in potential between the turns 16 and 20 being a function of the number of turns in the layers 17 and 19. By way of specific example, the layers may each have 350 turns, or the layers may be pyramided with the layers 17, 19, 23 and 25 having progressively fewer turns than layer 13. -Resistors in accordance with the present invention generally have power ratings of the order of 1/2 watt.

Figures 4 and 5 illustrate the resistance element of Figure 1 embedded in an epoxy resin case 60. As illustrated in Fif'ure 4, the case 60 may be provided with suitable mounting apertures such as 61 for fastening the case 69- in flat extended surface contact with a chassis surface 62 by means of suitable fastening means 64 as shown in Figure 5. The epoxy resin case is of a thickness to properly control the capacitive effect between the resistance element 47 and the chassis 62. This type of mounting gives very advantageous heat dissipation characteristics to the resistor, as well as providing a very compact assembly with the chassis. For example, the resistor may advantageously extend the entire length of the chassis in conforming contact therewith in certain applications.

A very advantageous manner of connecting t0 the resistance wire 11 is indicated in Figure 4 wherein a conductor 67 of circular cross section and of relatively large diameter as compared with the conductive portion 48 of wire 11 has a flattened end portion 63 bent into hook shape and mechanically clamped to the end of the conductive portion 48 of resistance wire 11,. This method provides extended conductive contact betweenthe terminal 67 and the wire 11 without requiring brazing or silver soldering -of the parts which embrittles the wire.

The epoxy resin recommended for use in embedding the resistance element 47 requires no pressure molding or high temperature, and thus avoids danger of damage to the wire in the molding or forming of the case 60 about the resistance element. The resistor need not be in actual contact with the chassis 62 as indicated in Figure 5, since advantageous heat dissipation effects are achieved even where the resistor has a broad at surface spaced from the iiat surface of the chassis. The casing 60 may have a glass fiber mesh embedded therein for added strength and for reinforcement of the mounting holes 61, and under such circumstances the resistor may withstand extremely high accelerations and shocks. The epoxy'case 6i) occupies the entire space about the resist.- ance element, or in other words the resistance element is encapsulated in the resin to eliminate air pockets adjacent the element. The case 60 thus prevents the formation of moisture near the resistance element, and the consequent possibilities of corrosion and the like.

The tube or tape 10 might also advantageously be i formed of glass fiber or the like insuch a way that upon forming of the case 60, the material of the casing would ow into the space between the plies corresponding to a and 10b in Figure 3 of the glass fiber and interlock the same. However, whether the tube or tape is of glass ber or a plastic such as polyethylene, it provides a relatively soft pliable surface free from sharp edges on which to m-ount the relatively fine resistance wire 11. Also relative expansion and contraction of the tube or tape and wire will not endanger the wire because the material of which the tube or tape is made will readily bend or constrict to accommodate relative contraction of the wire. This attribute of the tube or tape has the further advantage of enabling the resistance element to be bent or folded as needed to meet space requirements.

It will be understood that instead of having two terminals such as 71 and 72 between successive pies such as 43 and 44 in Figure 4, a single terminal may be connected to a conductor such as 27 extending between the pies, without cutting the conductor connecting successive pies as is done in Figure 4.

In Figure 1, if the spacing between successivel piessuch as 43 and 44 designated x, is equal to or greater than the longitudinal dimension y of the succeeding pi such as 44,` the resistance element 47 may be folded as illustrated in Figure 6. In Figure l, the arrows 80 indicate the direction of the magnetic fields of the successive pies in their straight condition, and it will be observed that the magnetic fields are all in the same direction. Hence, they tend to add in the lengthwise direction, although of course they are relatively small because of the close spacing of the conductor portions yon opposite sides of the tape as illustrated in Figure 3. To further'reduce the inductive effect of the resistance element,` the flattened tube or tape 10 may be folded as illustrated in Figure 6 to reverse the direction o-f the magnetic fields in alternate pies such as 44 and 46 relative to the pies 43 and 45, thereby opposing the magnetic fields of adjacent pies as well as providing a longitudinally more compact resistance ele-ment which for convenience will be designated by the reference numeral 81. It is to be understood that while for clarity Figure 6 shows the pies in more or less staggered or stepped relation, in actual practice they would be flattened to lie between closely spaced parallel planes. As with element 47 of Figure l, a flexible attened insulating tube could be slipped over the resistance element 81 of Figure 6 to form a flexible resistor.

As illustrated in Figure 7, the resistance element 81 could be embedded in an insulating case 88 of epoxy resin and the case 88 may be of a fiat rectangular configuration for mounting in close proximity to a chassis 90 or the like for optimum heat dissipation. Terminals 8S and 86 may have flat end portions such as 87 crimped over and pressed against the resistor wire end portion 48 in the same manner as in Figure 4. The case 88 may have mounting holes extending therethrough as illustrated in Figure 4 at 61, or the case 88 may be clamped to the chassis 90 or simply pressed thereagainst. The case may have a reinforcing skeleton of fiber glass or the like embedded therein for added strength as with the previously described embodiment.

Figures 8, 9 and l0 represent one manner in which the resistance element of Figures l, 2 and 3,-or Figure 6 may be formed for center hole mounting should such be desired. The element 47 or 81 is folded on a longitudinal axis into generally U or V cross section. The number of layers o-r the number of pies used on the element 47 or 81 may be selected in accordance with the size of the resistor to be formed. In the embodiment of Figure 8, each turn of wire such as indicated at 15 in Figure 2 is of an elongated loop form bent about a mid-point so that the opposite ends of the loop are folded toward eachother to form four wire segments with the current owing in successively opposite directions in the four segments to further neutralize the inductive effects of the wire as well as to render the 6' resistance element more compact in width. By way of illustration, a single conductor turn is illustrated in Figure 8a with arrows indicating the direction of current ow in the four successive segments 95a, 95b, 95e

`and 95d of the conductor 95. A resistance element of the type shown at 47 or 81 with the tape folded on a longitudinal axis is designated by the reference numerall 96 and is illustrated in cross section and end elevation in Figure 8. The element 96 may be used as a resistor in straight form in the same manner as elements 47 and 81, or may be disposed in a straight flattened flexible tube of insulating material as described in connection with the embodiments of Figures l and 6. Alternatively, the resistance element 96 may be wrapped arcuately about the core 97 of a spool 98 as illustrated in Figure 8. By way of illustration in Figures 8 and 9,v terminal lugs 100 and 101 may have portions such as 100a in Figure 9 encircling the core 97, and may have at lugs such as 10017 struck out and hooked to receive the respective ends of the resistance wire, such as 48 in Figure 9, for mechanically clinching the wire end portion 48 in the flat hook portion of the lug 100 in good electrical contact therewith.

Figure l0 indicates the manner in which the subassembly of Figures 8 and 9 would be embedded in an insulating case 102, with the center mounting hole 103 extending through the spool 98 and through the case 102 and with the terminal lugs such as 101 projecting from the case 102. By way of example, the case 102 may be in a cubical or other rectilinear form, and both the cases of Figure 7 and Figure l0 may be of epoxy resin.

Figure ll illustrates an element of the type shown at 47 or 81 folded on a longitudinal axis as in Figure 8 with the resistance wire wound thereon as illustrated in Figures l to 3 and with the folded resistance element wrapped helically onto a cylindrical tube 106. The final product may be identical to that shown in Figure 10', except that the casing 102 would be more elongated to accommodate the additional length of the tube 106.

The resistance element 47 or 81 may of course be wrapped around a core such as 97 in Figure 8 without first folding the element on a longitudinal axis, and the element may be wrapped helically about a tube such as 106 in Figure l-l without lirst folding the element along a longitudinal axis. -Any suitable means could be utilized to maintain the element 81 of Figure 6 in its folded condition as it is wrapped about the hub 97 or tube 106, for example a flattened flexible tube of insulating material could be slipped over the element 81, before it is wrapped into either of the arcuate configurations specified.

Each of the above mentioned modifications could, of course, be enclosed in a suitable insulating housing as illustrated in Figure l0, for example, or as illustrated in Figures 4 and 5, whichever is more suitable or advantageous.- In each case, the casing is preferably of epoxy resin and lls the entire space adjacent the resistance element.

Figure l2 illustrates an embodiment wherein the resistance element 47 of Figure l is cut along severance lines such as indicated by the dotted lines 115, 116 and 117 in Figure 1, and the resulting segments 118, 119, 120 and 121 with their respective tape portions 10a, 10b, 10c and 10d and pies 43, 44, 45 and 46 are turned through 90 in opposite directions to cause the magnetic axes of pies 43 and 45 to extend in the opposite direc` tion from the magnetic axes of the pies 44 and 46. The resulting element designated by the reference numeral 122 could be suitably secured to a flexible strip of insulating material as by stapling or cementing to form a flexible resistance element, or the resulting configura tion could be embedded in an insulating casing in the manner illustrated in Figures 4 and 5. Alternatively, the segments 118 and 120 in Figure l could be maingemme tained in the orientation illustrated in Figure l after severance along the lines 115, 116 and 117,*and the segments 119 and 1.21 could be turned through 180 to direct the magnetic axes of' the pies 44 and 46 in the longitudinal direction but in the opposite sense to the magnetic axis of the pies 43 and 45. In this case, the magnetic axes would be directly in line and opposing rather than being offset and extending in opposite directions as in Figure 12. Here again, the resulting configuration could be secured to a flexible insulating tape, or embedded in an insulating casing as just mentioned.

Referring to the embodiment of Figures 13 to 18, there is provided an elongated flexible flat tape 210 of insulating, or non-conductive material, such as paper or the like. The elongated tape 210 has a Width which is very much greater than the thickness of the tape as can be seen by comparing Figure 15 with Figure 18. An elongated resistance wire 212 is wound onto the flexible insulating tape 21d. The wire is wound into elongated loops and the successive loops of the winding defines what could be considered an elongated helical coil having elongated loops therein.

Insulated Wire is employed and the wire may, if desired, be coated with wax, oil, or the like before being wound onto the insulating tape. A continuous process is used, and so, for example, the tape 210 may be drawn off a roll therefor (not shown) and the wire is formed and wound about the tape as the tape is being withdrawn. By this means a continuous length of resistance element, comprising the tape 210 and the wire 212 Wound thereon is produced. In order to form a resistance unit of some desired resistance value, the circuit resistance of the resistance element so formed may be calibrated in lengths so that a partiuclar length of tape with a particular size resistance element wound thereon produces a desired, or particular, resistance.

After a segment of insulating tape with wire wound thereon has been cut to a desired length, that resistance element is preferably wound into a spiral 214 as shown in Figure 16, and the spiral 214 is inserted into a tubular insulating housing 216 formed of ceramic or the like. The spiral 214 has the ends 218 and 220 of the resistance wire 212 extending therefrom. The ends 218 and 220 of the resistance wire 212 are adapted to extend outwardly through the ends of the housing 216 and are connected mechanically or by soldering to terminals 222 and 224. In the preferred embodiment disclosed, the resistor R is completed by the attachment of terminals 222 and 224 to the ends of the housing 216 by inserting said terminals into the housing 216. The terminals 222 and 224 may be provided with enlarged terminal. ends, calibrated to the inner diameter of the housing 216, for engaging the leads 21.8 and 229 of the electrical resistance to provide good electrical contact between the ends of the resistance wire and the terminals. If desired, the terminals may be soldered to the housing, as generally indicated at 226, to provide greater strength for the resist-or and to seal the resistor unit against ingress of moisture or foreign material. Where porcelain housing and body members are used, the end portions thereof may be coated with copper or other metals to facilitate soldering. The unit when completed is also a very rugged unit in which the desired resistance value can be accurately maintained with a minimum of inductive effect.

In the construction shown in Figure 19, the resistor is inmost respects similar to the resistor shown in Figures 14 and 17 except that the resistance clement 228 in the housing is folded into pleats in accordion fashion rather than being wound in a spiral as shown in Figure 17. A perspective view of the accordion pleated resistance element of Figure 19 is also shown in Figure 20.

In all of the resistor units described herein, it will be noted that the resistance element comprises an elongated wire whose length can be accurately controlled to Vcontrol the resistance value thereof, and the resistance element formed with allat flexible tape having the resistance wire wound thereon; A length of resistance element so con- In the embodiments of Figures 13 to 20, it will be noted that the resistance element of the resistor is formed so that segmental lengths of the tape 219, with the resistance wire 212 wound thereon lie in stacked relation adjacent each other and the disposition of the loops of wire is such as to reduce reactive capacity effects of the resistor. In the case of the spiral, the stacked segments are adjacent arcs of the spiral, and in the case of the pleated resistance element, the stacked segments are the adjacent segments of the pleat.

It will be understood that the embodiments of Figures 13 to 20 could be formed on a flattened tube of insulating material just as in the embodiments of Figures l to 12. The embodiments of Figures 13 to 2O could have multiple layers as in Figure 2, or the embodiments of Figures l to 12 could comprise a tape of single thickness, or a flattened tube construction with a single layer winding.

The present application is a continuation-in-part of my copending application, Serial No. 458,384, filed September 27, 1954, now abandoned.

While numerous embodiments of the invention have been shown and described herein, it will be understood that they are illustrative only and not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

I claim as my invention:

1. An electrical resistor comprising tape means, electrical resistance means extending along said tape means, Aand said tape means having longitudinal segments thereof in a generally V configuration, with points of the resistance means representing the highest potential difference between the respective segments having the greatest spacial separation, and an insulating material disposed between said segments.

2. An electrical resistor comprising tape means, and a length of resistance Wire wound on said tape means in spaced groups of turns with successive groups of turns spaced ap-art by a distance at least substantially equal to the length of the respective groups.

3. An electrical resistor comprising tape means, a length of resistance wire tightly wound on said tape means, and an insulating casing substantially completely occupying the space surrounding said tape means and wire to eliminate the effects of humidity on the wire, said wire having an insulating coating thereon to prevent short circuits between adjacent turns thereof and said tape means having a cross section of loop configuration.

4. The method of making a fixed precision type wire wound resistor which comprises forming a thin walled tube of highly pliable insulating material, with the tube having a precise predetermined perimeter, winding a length of resistance wire helically on said tube, flattening said tube together with the resistance wire wound thereon into a tape-like resistance element, and completely embedding the resistance element in a rigid insulating casing.

5. The method of making an electrical resistor which comprises, winding a length of resistance wire transversely about a length of highly pliable insulating material in groups of turns of substantially equal length with said groups spaced apart a distance greater than the length of one of said groupsof turns, and folding said one group ofturns toward an adjacent group of turns-tto reversev the aiarajrasVy magneti-c axis of said one group of turns with respect to the magnetic axis of said adjacent group of turns.

6. The method of making an electrical resistor which comprises, winding a length of resistance wire helically on a thin walled tube of highly exible insulating material, liattening said tube and the resistance wire thereon to form a tape-like resistance element, and folding said resistance element on a longitudinal axis to reduce the transverse space requirements of the element.

7. The method of making an electrical resistor which comprises, winding a length of resistance wire helically on a thin walled tube of highly pliable insulating material, tlattening said tube with the resistance wire thereon to form a tape-like resistance element, folding said resistance element on a longitudinal axis to reduce the transverse space requirements of the unit, and wrapping the thus folded element into an arcuate configuration.

8. The method of making an electrical resistor which comprises, placing a length of material in a generally open loop conliguration, winding a length of an elongated resistance element helically on said length of material in spaced groups of turns,tiattening said length of material and the resistance element thereon into a tape-like resistance unit, and severing said length of material between adjacent groups of turns and shifting the resultant seg- -ments of the resistance unit to cause successive groups of turns to have 'magnetic axes extending in opposite directions.

9. An electrical resistor comprising: a thin walled tube of pliable plastic insulating material; and a precise predetermined length of resistance wire wound upon said tube in spaced apart groups of turns, said groups of turns being substan-tially equal in length and adjacent groups of turns being spaced aparta distance greater than the length of one group.

10. An electrical resistor comprising: tape means, and a length of resistance wire wound on said tape means in spaced groups of turns, which groups are of substantially equal length and spaced apart along the length of the tape means a distance substantially no less than the length of one group of turns, said tape means with the spaced apart groups of turns thereon forming a resistance element which is divided into a plurality of longitudinally spaced apart segments, and said resistance element being folded upon itself about a longitudinal axis.

l1. The electrical resistor of claim 10 further characterized by the fact that said folded resistance element is formed arcuately about a hollow core.

12. The electrical resistor of claim 11 further characterized by the fact that said folded and arcuately formed resistance element is encapsulated in a rigid casing of insulating material.

13. An electrical resistor comprising an insulating housing, an elongated resistance wire wound onto a flexible tape which in turn is rolled into a spiral so as to substantially neutralize the inductance effects in the resistance wire, and positioned in said housing, and the ends of said wire projecting in opposite directions from the spiral Within said insulating housing.

14. An electrical resistor comprising an elongated tubular insulating housing, an elongated resistance wire wound onto a tiexible tape which in turn is rolled into a spiral so as `to neutralize the inductance eifects in the resistance wire, and is positioned in said housing, so that the axis of the spiral is disposed parallel to the longitudinal axis of said housing, the ends of said wire projecting from the spiral, and terminals projecting in opposite directions beyond the housing and electrically connected to said ends of the wire.

15. An electrical resistor comprising: a coil support in the form of a length of tape-like insulating material folded upon itself on at least two transverse bend lines so that said coil support has at least one straight middle portion between said bend lines and two end portions, each overlying a part of the middle portion; a coil of resistance wire wound transversely upon the medial part of said middle portion of the support; and a coil of resistance wire wound transversely upon each of said two end portions of the coil support, each with one end thereof contiguous to one end of the coil on said middle portion of the said support and its other end contiguous to one end of said middle portion of the coil support so that said coils are endwise adjacent and their combined length substantially equals the length of said middle portion of the coil support; the winding direction of adjacent coils being opposite.

16. The method of making an electrical resistor having minimum inductance and capacitance which cornprises: winding a precise length of resistance wire transversely about a tube of highly pliable insulating material in groups of turns of substantially equal length with the convolutions of all of the turns running in the same direction and with said groups of turns spaced apart a distance greater than the length of one of said groups of turns; flattening the tube of insulating material with the wire wound thereon to collapse the tube and give it the formation of a multi-ply tape and to dispose the convolutions of the turns in closely adjacent substantially straight stretches at opposite sides of said multi-ply tape; and folding the multi-ply tape about transverse bend lines upon itself to superimpose portions of the tape which have no windings thereon upon adjacent groups of turns in endwise juxtaposition but endwise reversed from their original relationship so that the magnetic fields of adjacent groups of turns oppose one another.

17. The method of making an electrical resistor having a minimum of inductance and capacitance which comprises: winding a plurality of endwise spaced apart coils of resistance wire upon an elongated flexible support, with all of the coils wound in the same direction; and folding the liexible support about transverse bend lines upon itselt` to superimpose portions of the support having no coils thereon upon adjacent coils and to dispose adjacent coils in endwise juxtaposition but endwise reversed from their original relationship so that the magnetic fields of adjacent coils oppose one another.

18. A resistor of the character described comprising: a resistance element consisting of a spirally rolled length of pliant electrically non-conductive tape with a length of resistance wire wound transversely on and cemented to the tape; a tubular container of insulating material enclosing said element; and terminals connected to the ends of the resistance wire and projecting to the exterior of the container.

19. For use in making resistors of the character described: a section of pliant electrically non-conductive tape; and a length of resistance wire transversely wound on and cemented to the tape; the wire-wound tape being folded on a longitudinal axis substantially in the middle thereof, and also being rolled lengthwise into a compact unit.

20. A method of making resistors consisting in: winding resistance wire transversely on-and cementing the same to flexible electrically non-conductive tape; and forming the wire-wound tape lengthwise into a spiral roll suitable for insertion into a container.

21. A method of making resistors consisting in: winding resistance wire transversely on llexible electrically non-conductive tape in predetermined spaced windings and cementing the windings to the tape, so that the length of the wire-wound tape is an accurate measure of the resistance value of the amount of wire Wound thereon; cutting the wire-wound tape to a length corresponding to the total resistance required; and rolling the thus cut length of wire-wound tape lengthwise into a compact spiral roll.

(References on following page) Referencgs Cited in the le of this patcnt UNITED STATES PATENTS Ingersoll Nov. 30, 1915 Stoekel June 24, 1930 Pugh Oct. 9, 1934 Schellenger Nov. 5, 1935 Hastings Nov. 19, 1935 12 Dike' Jan. 7, Ogg July 14, Crosby Mar. 26, Smith et al. Mar. 1, Cloud Nov. 8, Levers et al Ian. 15, Sarno Nov. 24, Koenig Jan. 3, Wholly Dec. 2, 

